package org.apache.lucene.search;

/**
 * Copyright 2004 The Apache Software Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import org.apache.lucene.index.IndexReader;

import java.io.IOException;

/**
 * A range query that returns a constant score equal to it's boost for
 * all documents in the range.
 * <p>
 * It does not have an upper bound on the number of clauses covered in the range.
 * <p>
 * If an endpoint is null, it is said to be "open".
 * Either or both endpoints may be open.  Open endpoints may not be exclusive
 * (you can't select all but the first or last term without explicitly specifying the term to exclude.)
 *
 * @author yonik
 * @version $Id$
 */

public class ConstantScoreRangeQuery extends Query {
    private final String fieldName;
    private final String lowerVal;
    private final String upperVal;
    private final boolean includeLower;
    private final boolean includeUpper;

    public ConstantScoreRangeQuery(String fieldName, String lowerVal, String upperVal, boolean includeLower, boolean includeUpper) {
        // do a little bit of normalization...
        // open ended range queries should always be inclusive.
        if (lowerVal == null) {
            includeLower = true;
        } else if (includeLower && lowerVal.equals("")) {
            lowerVal = null;
        }
        if (upperVal == null) {
            includeUpper = true;
        }

        this.fieldName = fieldName.intern(); // intern it, just like terms...
        this.lowerVal = lowerVal;
        this.upperVal = upperVal;
        this.includeLower = includeLower;
        this.includeUpper = includeUpper;
    }

    /** Returns the field name for this query */
    public String getField() {
        return fieldName;
    }

    /** Returns the value of the lower endpoint of this range query, null if open ended */
    public String getLowerVal() {
        return lowerVal;
    }

    /** Returns the value of the upper endpoint of this range query, null if open ended */
    public String getUpperVal() {
        return upperVal;
    }

    /** Returns <code>true</code> if the lower endpoint is inclusive */
    public boolean includesLower() {
        return includeLower;
    }

    /** Returns <code>true</code> if the upper endpoint is inclusive */
    public boolean includesUpper() {
        return includeUpper;
    }

    public Query rewrite(IndexReader reader) throws IOException {
        // Map to RangeFilter semantics which are slightly different...
        RangeFilter rangeFilt = new RangeFilter(fieldName, lowerVal != null ? lowerVal : "", upperVal, lowerVal == "" ? false : includeLower, upperVal == null ? false : includeUpper);
        Query q = new ConstantScoreQuery(rangeFilt);
        q.setBoost(getBoost());
        return q;
    }

    /** Prints a user-readable version of this query. */
    public String toString(String field) {
        StringBuffer buffer = new StringBuffer();
        if (!getField().equals(field)) {
            buffer.append(getField());
            buffer.append(":");
        }
        buffer.append(includeLower ? '[' : '{');
        buffer.append(lowerVal != null ? lowerVal : "*");
        buffer.append(" TO ");
        buffer.append(upperVal != null ? upperVal : "*");
        buffer.append(includeUpper ? ']' : '}');
        if (getBoost() != 1.0f) {
            buffer.append("^");
            buffer.append(Float.toString(getBoost()));
        }
        return buffer.toString();
    }

    /** Returns true if <code>o</code> is equal to this. */
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (!(o instanceof ConstantScoreRangeQuery))
            return false;
        ConstantScoreRangeQuery other = (ConstantScoreRangeQuery) o;

        if (this.fieldName != other.fieldName // interned comparison
                        || this.includeLower != other.includeLower || this.includeUpper != other.includeUpper) {
            return false;
        }
        if (this.lowerVal != null ? !this.lowerVal.equals(other.lowerVal) : other.lowerVal != null)
            return false;
        if (this.upperVal != null ? !this.upperVal.equals(other.upperVal) : other.upperVal != null)
            return false;
        return this.getBoost() == other.getBoost();
    }

    /** Returns a hash code value for this object.*/
    public int hashCode() {
        int h = Float.floatToIntBits(getBoost()) ^ fieldName.hashCode();
        // hashCode of "" is 0, so don't use that for null...
        h ^= lowerVal != null ? lowerVal.hashCode() : 0x965a965a;
        // don't just XOR upperVal with out mixing either it or h, as it will cancel
        // out lowerVal if they are equal.
        h ^= (h << 17) | (h >>> 16); // a reversible (one to one) 32 bit mapping mix
        h ^= (upperVal != null ? (upperVal.hashCode()) : 0x5a695a69);
        h ^= (includeLower ? 0x665599aa : 0) ^ (includeUpper ? 0x99aa5566 : 0);
        return h;
    }
}
